The invention relates generally to hot melt adhesive dispensing systems, and more particularly to apparatuses for pre-heating air supplied to one or more hot melt adhesive dispensing nozzles mounted on a manifold supplying adhesive thereto.
In hot melt adhesive dispensing systems pre-heated air is used to control the dispensing of adhesives through one or more adhesive orifices of an adhesive dispensing nozzle. The pre-heated air is dispensed from one or more air orifices associated with each adhesive orifice to add heat to adhesive dispensed therefrom. The preheated air may also modify the flow of adhesive dispensed from the adhesive orifice, for example, to form and dispense adhesive fibers in swirling spiral patterns and also to form and dispense vacillating meltblown adhesive fibers. It is also desirable to pre-heat air and fluids for use in many other manufacturing operations.
U.S. Pat. No. 5,145,689, issued on Sep. 8, 1992, entitled "Meltblowing Die", discloses one known air pre-heating apparatus for meltblowing dies that dispense hot melt adhesives. The pre-heating apparatus comprises an air supply conduit having an axially disposed insulator core with a heater coil wound thereabout and along an axial dimension thereof. The heater coil extends radially outwardly from the insulator core toward an interior surface of the conduit and transfers heat to air flowing therethrough, whereby the pre-heated air is supplied to the meltblowing dies.
The referenced U.S. application Ser. No. 08/683,064, entitled "Hot Melt Adhesive Applicator With Metering Gear-Driven Head" discloses another known air pre-heating apparatus for hot melt adhesive dispensing systems comprising a common air supply conduit coupled to a plurality of parallel conduits disposed over several heating members. The plurality of parallel air supply conduits provide relatively increased surface area to improve heat transferred from the heating members to air.
The known prior art air pre-heaters suitable for hot melt adhesive dispensing applications, however, pre-heat air relatively inefficiently. Additionally, many hot melt adhesive dispensing systems include generally a heated manifold that supplies hot adhesive to the one or more adhesive dispensing nozzles coupled thereto. In some systems, the air pre-heating apparatus is coupled directly to the heated manifold. The pre-heated air may be supplied to the nozzles through conduits in the heated manifold. It is often desirable, however, to maintain the temperature of the pre-heated air supply at a temperature different than that of the heated manifold to optimally control adhesive dispensed from the nozzles. Prior art systems that mount the air pre-heater directly on the manifold, or supply the pre-heated air through the manifold to the nozzle, may increase or decrease the temperature of the pre-heated air supply, thereby adversely affecting the dispensing of fluid from the nozzles.
The present invention is drawn toward advancements in the art of preheating fluids, and more particularly to pre-heating air supplied to one or more hot melt adhesive dispensing nozzles mounted on a manifold, and combinations thereof.
It is an object of the invention to provide a novel fluid pre-heating apparatus useable for preheating air supplied to one or more hot melt adhesive dispensing nozzles mounted on an adhesive supply manifold, and combinations thereof, that are economical and that overcome problems in the prior art.
It is another object of the invention to provide a novel air pre-heating apparatus that preheats air relatively efficiently by supplying ambient air from an air supply inlet of the apparatus, through the apparatus against a decreasing temperature gradient therein, and to an air supply outlet of the apparatus, whereby heat is increasingly added thereto before the air is discharged from the air supply outlet.
It is a more particular object of the invention to provide a novel air pre-heating apparatus having an air supply inlet on or at least proximate an outer portion of an outer heating member and an air supply outlet on an inner heating member having a heater therein. The outer heating member comprises generally a plurality of laminated plates having one or more air flow paths, which preferably include one or more serpentine air flow path portions that increase the residence time of the air therein. The air is supplied from the air supply inlet, and through the apparatus against a decreasing temperature gradient, whereby heat is increasingly added thereto before the air is discharged from the air supply outlet of the apparatus, which may be coupled to an adhesive dispensing nozzle.
It is a further object of the invention to provide a novel fluid pre-heating apparatus useable for pre-heating air supplied to one or more hot melt adhesive dispensing nozzles mounted on an adhesive supply manifold, wherein the air pre-heating apparatus is thermally isolated from the manifold to permit maintaining the pre-heating apparatus at a temperature different than a temperature of the manifold.
These and other objects, aspects, features and advantages of the present invention will become more fully apparent upon careful consideration of the following Detailed Description of the Invention and the accompanying Drawings, which may be disproportionate for ease of understanding, wherein like structure and steps are referenced generally by corresponding numerals and indicators.